I am stumped as to the way these thigns operate. On my 2001 V70, the radiator fan has a controller mounted on it, that get supplied 12v at all times, and alos has a purple thin wire going to it. If you ground the wire for a sec or something, the fan spins for a 1/2 sec or so(really slow spinup 50rpm?).. then shuts off. Can anybody tell me how this thing works? What does the wire do? does the controller have built in temp sensor to turn on the fan when the temp gets too high, and depending on how fast it cools down.. that tells it wether or not to spin up to full speed.

My only guess for the purple wire is when the car turns on.. it sends a quick pulse to see if the fan works, then as the fan turns on, then spins down, the thing acts like a generator, and sends a quick pulse back to the ECU telling it that the thing works fine.

The reason I want to know all this, is that I won an s80 fan on ebay for 51 w/shipping, that includes the shrouding, fan, and controller. I want to maybe use the controller to operate the fan on my car with little or no modification. My goal is get the fan to operate at low speed full time when the AC is on, then to spin up to high when the engine gets too hot. Maybe I could mod the controller a wee bit to acheive these goals. If you have information on this.. or have had the balls to tinker with your new car in the goal to figure out how things work let me know

Kevin